The present invention relates to a cloth cleaning device and a polishing machine including the cloth cleaning device.
A surface of a semiconductor wafer must be precisely polished like a mirror face with uniform thickness before integrated circuits are formed thereon.
Many types of polishing machines have been used to polish semiconductor wafers, etc.
One of the conventional polishing machines is shown in FIGS. 8 and 9. The polishing machine 10 has a polishing plate 12 having an upper face which is covered with a polishing cloth and which is rotated in a horizontal plane. A center roller 14, which is capable of rotating freely, is arranged at a center of the polishing plate 12. A plurality of work plates 16 are arranged on the polishing cloth. Work pieces to be polished, e.g., semiconductor wafers, are adhered to a bottom face of each work plate 16, and their bottom faces contact the polishing cloth.
FIG. 10 shows a state in which the semiconductor wafers 17 are adhered to the work plate 16. Guide rollers 18 are arranged in the vicinity of an outer edge of the polishing plate 12 as shown in FIG. 9, and outer circumferential faces of the work plates 16 contact the center roller 14 and the guide rollers 18. The polishing plate 12 is rotated in a direction of an arrow xe2x80x9cAxe2x80x9d, but the work plates 16 are held at predetermined positions by the center roller 14 and the guide rollers 18.
As shown in FIG. 9, the guide rollers 18 are moved vertically by an elevating mechanism, and their strokes of vertical movement are equal to or more than the thickness of the work plates 16. When the guide rollers 18 are at their lowest positions, they are located close to the outer edge of the polishing plate 12 so as to contact the outer circumferential face of the work plates 16 and when the guide rollers 18 are at their highest positions, they are moved away from the outer edge of the polishing plate 12 so as to allow the work plates 16 to pass through a space between the center roller 14 and the guide rollers 18 with the rotation of the polishing plate 12.
The guide rollers 18 may be moved between positions close to the outer edge of the polishing plate 12 and positions away therefrom by, for example, swinging arms of the guide rollers 18. The moving mechanism of the guide rollers 18 is not always necessary. In some constructions, the guide rollers 18 may be fixed at predetermined positions or no guide rollers 18 are required.
Press heads 20 are moved vertically. When the press heads 20 are at their lowest positions, the press heads 20 respectively press the work plates 16 and the semiconductor wafers onto the polishing cloth with an appropriate force. Therefore, the bottom faces of the semiconductor wafers can be polished by the polishing cloth which is rotated together with the polishing plate 12.
The press heads 20 can be freely rotated about their axes.
While polishing the semiconductor wafers, alkaline slurry including abrasive grains, e.g., silica grains, is fed to the rotating polishing cloth. Therefore, the bottom faces of the semiconductor wafers can be mechanically and chemically polished like mirror faces.
A holding member 23 is arranged on a front end of an arm 22 for enabling the polishing cloth to be cleaned. More specifically, a brush (not shown) for brushing the surface of the polishing cloth is arranged on a bottom face of the holding member 23.
The arm 22 is capable of swinging or rotating about a rotary shaft 24 which is located outside of the polishing plate 12. While the semiconductor wafers are polished, the arm 22 is located outside of the polishing plate 12 and while the polishing cloth is cleaned, the arm 22 is swung, about the rotary shaft, above the polishing plate 12.
To clean the polishing cloth, wash water is directed in a radial direction from the center roller 14 onto the polishing cloth.
The polishing cloth must be cleaned because abraded grains, which are formed by abrading the semiconductor wafers, and reaction products gradually permeate and deposit in the polishing cloth. As a result, the polishing efficiency of the polishing cloth is reduced during the course of its use.
However, in the conventional polishing machine, the polishing cloth is cleaned by merely supplying the wash water from the center roller 14 and brushing. As a result, the polishing cloth cannot be fully cleaned, and the polishing efficiency of the polishing cloth cannot be recovered. Further, the holding member 23 must have a prescribed width, so the holding member 23 must be moved backward from the center roller 14 so as not to collide with the center roller 14 when the arm 22 is swung, so that a part of the polishing cloth in the vicinity of the outer circumferential face of the center roller 14 cannot be cleaned well.
An object of the present invention is to provide a cloth cleaning device and a polishing machine which are capable of fully cleaning a polishing cloth including a part in the vicinity of a center roller.
To achieve this object, a cloth cleaning device of a polishing machine in accordance with the present invention comprises an arm movable in a plane parallel to a polishing cloth arranged on an upper face of a polishing plate between a first position, above the polishing cloth and a second position outside of the polishing cloth; a jet nozzle attached to the arm and arranged to direct high pressure water toward the polishing cloth; and an enclosing member enclosing the jet nozzle so as to prevent the high pressure water, which has been directed out from the jet nozzle, from scattering. The jet nozzle is headed or oriented toward a center roller arranged at the center of the polishing plate and the high pressure water is directed toward a part of the polishing cloth in the vicinity of the center roller when the arm moves the jet nozzle close to the center roller.
A polishing machine in accordance with the present invention comprises a polishing plate having an upper face covered with a polishing cloth; a driving mechanism for rotating the polishing plate; a center roller arranged at a center of the polishing plate; a work plate arranged on the polishing cloth and to which a work piece to be polished is adhered and whose outer circumferential face contacts an outer circumferential face of the center roller such that the work piece contacts the polishing cloth; a press head for pressing the work plate onto the polishing cloth; a slurry feeding mechanism for feeding slurry to the polishing cloth; an arm movable in a plane parallel to the polishing cloth between a first position above the polishing cloth and a second position outside of the polishing cloth; a jet nozzle attached to the arm and arranged to direct high pressure water toward the polishing cloth; and an enclosing member enclosing the jet nozzle so as to prevent the high pressure water which has been directed out from the jet nozzle, from scattering. The jet nozzle is headed or oriented toward the center roller and the high pressure water is directed toward a part of the polishing cloth in the vicinity of the center roller when the arm moves the jet nozzle close to the center roller.
The polishing machine may further comprise a guide roller arranged in the vicinity of an outer edge of the polishing plate, and an outer circumferential face of the work plate may contact outer circumferential faces of the center roller and the guide roller.
In the present invention, an angle of the jet nozzle may be changed between a first angle, at which the jet nozzle is headed toward the center roller, and a second angle, at which the jet nozzle is vertical with respect to the polishing cloth.
A sectional shape of a jet form of the high pressure water may be longer in the direction of moving the arm.
The enclosing member may be a plastic net enclosing the jet nozzle.
In the cloth cleaning device and the polishing machine of the present invention, the polishing cloth including the part in the vicinity of the center roller can be fully cleaned, so that the work piece can be precisely polished with a higher polishing efficiency and the longevity of the expensive polishing cloth can be increased.